A person's email address is a popular way to identify the person. Many newsletter operators only require an email address from a person to subscribe to a newsletter. Some website operators only require a user to provide an email address as the login identifier and the first name and last name are not required. It would be helpful for these operators to get some information about their users, e.g., genders, ethnic origins, geographic locations, job positions and industries. Such information can be used by the operator to improve services.
The limitation is that these operators only have the email addresses of their users but not their person names and most traditional profile databases do not support using email address as the search key. Some commercial service providers offer services to look up people by their email addresses. Examples of such service providers include Corporate Yellow Book, Jigsaw, Netprospex, Zoominfo, Emailfinder, Spokeo and Rapleaf. Their approach is to build up and maintain a proprietary database using government records, public records, public web sites, social website membership data, manual user submission and/or various online tracking technologies such as web browser cookies.
The approach of these commercial service providers has several challenges. The first challenge is that it requires significant time and effort to accumulate a database large enough to be useful. As a result many of them have only a relatively small number of email addresses and no service provider can guarantee that it can locate every email address. The second challenge is that it requires recurring effort to keep the database up-to-date. People change their email addresses but the data sources that these service providers originally rely upon to find the email addresses often do not get updated. Therefore the service providers have to cross-reference different data sources at different times to identify a person and update their records. The third challenge is that online tracking technologies can raise privacy concerns as witnessed by privacy-related lawsuits against some of these commercial service providers.